1. Field of the Invention
This invention generally relates to an image sticking elimination circuit, and more particularly to an image sticking elimination circuit suitable for sudden lost of power.
2. Description of Related Art
As shown in FIG. 5, the conventional LCD 500 includes a gate drive circuit 510, a data drive circuit 520, a plurality of gate lines 512, a plurality of date lines 522, and an array of display pixels each generally comprising a transistor 532, a capacitor 534 and a pixel cell 536. The gate line 512 and the data line 522 and associated components define a pixel unit 550. When the data signal is written (i.e., when the data signal is going to be displayed on the pixel unit 500), the gate drive circuit 510 will raise the gate line 512 from a low voltage level to a high voltage level so that the transistor 532 will be turned on. Then the data drive circuit 520 writes the data signal to the capacitor 534 via the data line 522 and the image corresponding to the data signal is displayed at the pixel cell 536. After the data signal is written into the capacitor 534, the gate drive circuit 510 will lower the gate line 512 from a high voltage level to a low voltage level so that the pixel cell 536 can maintain the image according to the data signal before the next data signal is written. However, once the abnormal power-off of the LCD 500 occurs (e.g., power-off of the display not by the pixel switches, but by sudden lost of power), the data signal is still stored in the capacitor 534. That is where the image sticking comes from.
The conventional solution to eliminate the image sticking shifts the I-V curve of the transistor 532 (as shown in FIG. 6) to the left so that the threshold voltage of the transistor 532 is close to 0V. Hence the transistor 532 can be turned on even if the gate voltage of the transistor 532 is close to 0V so that the data signal stored in the capacitor 534 can be released to the data line 522. The image sticking problem does not occur, however, the current leakage occurs instead due to the decreased threshold voltage.